DESCRIPTION: Alcoholism remains a major public health problem, costing the nations billions annually through medical complications, accidents, alcohol-associated violence, and lost productivity. An improved molecular understanding of the pathogenesis of alcoholism and its neurological complications is needed to improve prevention and treatment. Mental retardation, hydrocephalus, and agenesis of the corpus callosum are observed both in fetal alcohol syndrome (FAS) and in children with mutations in the gene for the cell adhesion molecule (CAM) L1. We have observed that low concentrations of ethanol (IC50 7 mM) inhibit cell-cell interactions mediated by Ll, but have no effect on adhesion mediated by a related molecule, N-CAM. Because Ll plays a fundamental role in long-term potentiation, learning, and nervous system development, perturbation of L1-mediated cell-cell adhesion and signaling could contribute to memory disorders in alcoholics and FAS. We propose to use selective mutagenesis of the human cDNA for L1 to study the molecular basis for ethanol's inhibition of L1-mediated cell-cell adhesion. We will create deletion mutants of the human L1 cDNA for mapping ethanol-sensitive domains that influence L1-mediated cell adhesion, tyrosine kinase activity, neurite elongation, and cerebellar migration. We will next express these Ll deletion mutants in NIH/3T3 fibroblasts and bacteria. We will determine whether individual adhesive immunoglobulin-like (Ig) or fibronectin type III repeat homology domains (FN3) of L1 exhibit ethanol-sensitive adhesiveness when expressed in NIH/3T3 cells, and will then learn whether specific deletions in the L1 cDNA abolish ethanol's inhibition of Ll-mediated cell-cell adhesion and morphogenesis. To explore whether the transmembrane and cytoplasmic domains of L1 are required for ethanol sensitivity, we will examine the effects of ethanol on the adhesion of Covaspheres coated with soluble L1-Fc chimeras. To learn whether ethanol sensitivity resides in the extracellular domain of L1, we will construct chimeric molecules of ethanol-insensitive N-CAM and ethanol-sensitive Ll by swapping the cytoplasmic/transmembrane domains and the extracellular domains of these two molecules. Our long-term objective is to understand the molecular mechanism by which ethanol interacts with Ll and other transmembrane proteins. This knowledge will improve our understanding of the pathogenesis of fetal alcohol syndrome and cognitive disorders in alcoholics, paving the way for more effective prevention and treatment of these disorders.